Sand control seal for subsurface safety valve

Abstract

A seal is provided to prevent contamination by sand or grit in the clearance between a flow tube and the inner housing wall in a safety valve. An enlarged space is provided adjacent the seal to allow accumulation of sand or grit in the annular clearance space without causing seizure of the flow tube. The insert safety valve is assembled without a spacer with a seal mounted to the lower end of the insert valve to engage the bottom sub on the SSV. As a result, particularly for larger sizes of insert safety valves, the assembly is lighter and shorter, which facilitates use of readily available standard lubricator and wireline equipment.

I claim:  
     
       1. A safety valve for downhole use, comprising: 
       a housing, comprising a flow passage therethrough;  
       piston movably mounted in said housing and connected to a flow tube for moving the flow tube in said housing to operate the valve;  
       said flow tube defining a clearance in said flow passage; and  
       a particulate retention device spanning said clearance;  
       said particulate retention device comprises a ring;  
       said ring is mounted in a groove;  
       said groove is sufficiently deep so that flexing of said housing will not bring an outer diameter of said ring in contact with a bottom of said groove.  
     
     
       2. The valve of  claim 1 , wherein: 
       said groove is disposed in said housing.  
     
     
       3. The valve of  claim 1 , wherein: 
       said groove is disposed in said flow tube.  
     
     
       4. The valve of  claim 1 , wherein: 
       said ring is split to facilitate mounting in said groove.  
     
     
       5. The valve of  claim 1 , wherein: 
       said clearance is enlarged adjacent said particulate retention device.  
     
     
       6. The valve of  claim 5 , wherein: 
       said enlargement is created by a recessed surface on said housing.  
     
     
       7. The valve of  claim 4 , wherein: 
       said ring is split in a plane intersecting the longitudinal axis of said housing.  
     
     
       8. The valve of  claim 1 , wherein: 
       said housing further comprises a pair of straddle seals to allow said housing to be sealingly inserted into an existing tubing safety valve without a spacer.  
     
     
       9. An insert safety valve for insertion and operation through a tubing safety valve, said tubing safety valve further comprising a nipple adapter and a bottom sub having an internal bore, and a control system passage with an access opening provided from said control system into said bore in anticipation of insertion of said insert safety valve, said insert valve comprising: 
       a valve housing having a pair of seals thereon positioned to engage said nipple adapter and said bottom sub in said bore of the tubing safety valve and straddle said opening, without the use of a spacer.  
     
     
       10. The insert safety valve of  claim 9 , wherein: 
       said housing further comprises a flow passage therethrough;  
       a piston movably mounted in said housing and connected to a flow tube for moving the flow tube in said housing to operate the valve;  
       said flow tube defining a clearance in said flow passage; and  
       a particulate retention device spanning said clearance.  
     
     
       11. The valve of  claim 10 , wherein: 
       said particulate retention device comprises a ring.  
     
     
       12. The valve of  claim 11 , wherein: 
       said ring is mounted in a groove.  
     
     
       13. The valve of  claim 12 , wherein: 
       said groove is disposed in said housing.  
     
     
       14. The valve of  claim 10 , wherein: 
       said clearance is enlarged adjacent said particulate retention device.  
     
     
       15. The valve of  claim 12 , wherein: 
       said groove is sufficiently deep so that flexing of said housing will not bring an outer diameter of said ring in contact with a bottom of said groove.